Conversion

import com.spire.doc.Document;
import com.spire.doc.FileFormat;
import com.spire.doc.documents.ImageType;

import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

public class ConvertDemo {

    public void convertDemo(String filePath, String convertTo, String resultFileName) throws IOException {
        Document document = new Document();
        document.loadFromFile(filePath);
        convertion(document,convertTo,resultFileName);
    }

    private void convertion(Document doc, String convertTo, String resultFileName) throws IOException {
        switch (convertTo) {
            case "PDF":
                doc.saveToFile(resultFileName+".pdf", FileFormat.PDF);
                break;
            case "XPS":
                doc.saveToFile(resultFileName + ".xps", FileFormat.XPS);
                break;
            case "IMAGE":
                BufferedImage[] images = doc.saveToImages(ImageType.Bitmap);
                if (images != null && images.length > 0){
                    if (images.length == 1){
                        ImageIO.write(images[0],".PNG", new File(resultFileName+".png"));
                    }else {
                        for (int j = 0; j < images.length;j++){
                            String fileName = String.format("image-{0}.png",j);
                            ImageIO.write(images[j],".PNG",new File(fileName));
                        }
                    }
                }
                break;
            case "RTF":
                doc.saveToFile(resultFileName+".rtf", FileFormat.Rtf);
                break;
            case "TIFF":
                doc.saveToTiff(resultFileName +".tiff");
                break;
            case "HTML":
				doc.getHtmlExportOptions().setImageEmbedded(true);
				doc.getHtmlExportOptions().setCssStyleSheetType(CssStyleSheetType.Internal);
                doc.saveToFile(resultFileName+".html", FileFormat.Html);
                break;
        }
    }
}

using System;
using System.Drawing;
using System.Drawing.Imaging;

using Spire.Doc;
using Spire.Doc.Documents;

namespace DemoOnlineCode
{
    class Convertors
    {
        public void demoConversion(String docFile, string format)
        {
            Document document = new Document(docFile, FileFormat.Auto);
            ConvertFormat(document, format);
        }

        private void ConvertFormat(Document document, string format)
        {
            switch (format)
            {
                case "PDF":
                    document.SaveToFile("demo.pdf", FileFormat.PDF);
                    break;

                case "XPS":
                    document.SaveToFile("demo.xps", FileFormat.XPS);
                    break;

                case "Image":
                    Image[] Images = document.SaveToImages(ImageType.Bitmap);
                    if (Images != null && Images.Length > 0)
                    {
                        if (Images.Length == 1)
                        {
                            Images[0].Save("demo.bmp", System.Drawing.Imaging.ImageFormat.Bmp);
                        }
                        else
                        {
                            for (int i = 0; i < Images.Length; i++)
                            {
                                String fileName = String.Format("Image-{0}.png", i);
                                Images[i].Save(fileName, ImageFormat.Png);
                            }
                        }
                    }
                    break;
                case "RTF":
                    document.SaveToFile("demo.rtf", FileFormat.Rtf);
                    break;
                case "TIFF":
                    Image[] TiffImage = document.SaveToImages(ImageType.Bitmap);

                    Image result = JoinTiffImages(TiffImage, EncoderValue.CompressionLZW);
                    result.Save("demo.tiff", ImageFormat.Tiff);
                    break;
                case "HTML":
					document.HtmlExportOptions.CssStyleSheetType = CssStyleSheetType.Internal;
					document.HtmlExportOptions.ImageEmbedded = true;
                    document.SaveToFile("demo.html", FileFormat.Html);
                    break;
            }
        }

        private static Image JoinTiffImages(Image[] images, EncoderValue compressEncoder)
        {

            //use the save encoder
            Encoder enc = Encoder.SaveFlag;
            EncoderParameters ep = new EncoderParameters(2);
            ep.Param[0] = new EncoderParameter(enc, (long)EncoderValue.MultiFrame);
            ep.Param[1] = new EncoderParameter(Encoder.Compression, (long)compressEncoder);

            Image pages = null;
            int frame = 0;
            ImageCodecInfo info = GetEncoderInfo("image/tiff");

            foreach (Image img in images)
            {
                if (frame == 0)
                {
                    pages = img;
                    pages.Save("demo.tiff", info, ep);
                }
                else
                {
                    //save the intermediate frames
                    ep.Param[0] = new EncoderParameter(enc, (long)EncoderValue.FrameDimensionPage);

                    pages.SaveAdd(img, ep);

                }

                if ((frame == images.Length - 1) && frame != 0)
                {
                    //flush and close.
                    ep.Param[0] = new EncoderParameter(enc, (long)EncoderValue.Flush);
                    pages.SaveAdd(ep);
                }

                frame++;
            }
            return pages;
        }

        private static ImageCodecInfo GetEncoderInfo(string mimeType)
        {
            ImageCodecInfo[] encoders = ImageCodecInfo.GetImageEncoders();
            for (int j = 0; j < encoders.Length; j++)
            {
                if (encoders[j].MimeType == mimeType)
                    return encoders[j];
            }

            throw new Exception(mimeType + " mime type not found in ImageCodecInfo");
        }
    }
}